共查询到20条相似文献,搜索用时 203 毫秒
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研究了纯铜多道次反复镦压剧烈塑性变形后的组织、力学性能及导电性能。结果表明,通过反复镦压能在保持试样原始形状和尺寸的情况下在材料内部累积很大的应变,实现材料组织的超细化,退火纯铜经B路线15道次反复镦压变形后,晶粒细化至亚微米级。随镦压次数的增加,纯铜的硬度和抗拉强度明显提高,抗拉强度达到459.1MPa,伸长率明显下降,但仍在20%以上。纯铜的导电率随镦压次数的增加而下降,但15道次镦压后仍然保持在91.7%IACS,说明反复镦压剧烈塑性变形工艺可以制备出具有高强度和良好导电性的块体纯铜材料。 相似文献
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在道次之间试样不旋转(A)和道次之间试样90°顺时针旋转(B)两种路径下对7003铝合金进行了4道次等通道侧向挤压(DECLE),研究了挤压变形后合金的显微组织和力学性能。结果表明:7003铝合金经4道次DECLE处理后,晶粒均细化至纳米级;A路径下合金中形成了平行弯曲状剪切带,B路径下形成了交叉状剪切带,交叉状剪切带对位错的分割作用更好地细化了晶粒;两种路径下合金的屈服强度、抗拉强度和硬度均随着DECLE道次的增加而增大,B路径下的强度和硬度均高于A路径下的,但断后伸长率低于A路径下的。 相似文献
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对T4态和T6态WE54合金进行准静态压缩变形和空气锤锻(高速)变形试验,研究了变形前后的显微组织、硬度和压缩性能.结果表明:T4态和T6态WE54合金在准静态变形和高速变形后,部分变形晶粒内出现孪晶,并且在一些粗大孪晶内形成了二次孪晶,孪晶出现平行排列和交割特征;不同速率变形后T4态和T6态合金的变形晶粒尺寸未发生明显变化,但新生成的孪晶由于切割基体细化了组织,有助于维氏硬度和压缩性能的提高;与准静态变形相比,高速变形能够促进晶粒采用孪生机制协调变形,产生更多的孪晶界细化组织,提升变形后合金的硬度和屈服强度. 相似文献
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通过KBF4与熔融铝反应制备了Al-4B中间合金,研究了不同质量分数(0%~2.0%)Al-4B中间合金作为孕育剂对AZ31镁合金晶粒尺寸和力学性能的影响.结果表明:Al-4B中间合金由AlB2和α-Al相组成;Al-4B中间合金的添加可以明显细化AZ31镁合金的晶粒,提高晶粒尺寸的均匀性,降低孔隙率,Al-4B中间合金质量分数为1.0%时,晶粒细化效果最明显;随着Al-4B中间合金含量增加,AZ31镁合金的硬度、抗拉强度、屈服强度和断后伸长率均增大,屈服强度与晶粒尺寸符合Hall-Petch关系,AZ31镁合金力学性能的改善主要与AlB2相产生的细晶强化、弥散强化以及铸造组织孔隙率降低有关. 相似文献
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F. Khodabakhshi M. Abbaszadeh S. R. Mohebpour H. Eskandari 《The International Journal of Advanced Manufacturing Technology》2014,73(9-12):1291-1305
A new modification of constrained groove pressing (CGP) process named as constrained groove pressing–cross route (CGP-CR) was suggested for severe plastic deformation (SPD) of sheet form metals with great potential for fabricating high strength nanostructured sheets. This process is based on the conventional CGP process including some modifications. One pass of this process includes eight stages (four corrugation and four flattening) and involves 90° cross-rotation between each two stages. As a result of each CGP-CR pass, a strain magnitude of ~2.32 is imparted to the sample. To simulate the process, finite element modeling (FEM) was carried out using three-dimensional finite element analysis ABAQUS/Explicit simulation. Strain and hardness distribution through the sheet after CGP-CR process at different stages were examined via FEM. Low-carbon steel sheet was utilized as the testing material and CGP-CR process imparted upon it up to two passes. Afterward, equivalent plastic strain was measured ~4.64. Results show that the magnitude and uniformity of strain were different along three main directions of sheets: rolling (RD), transverse (TD), and normal directions (ND), at different stages of process. In addition, the results indicate that, for the CGP-CR’d sheets up to two passes, the magnitude and uniformity of hardness simulated via FEM were consistent with the experimental data. 相似文献
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Thomas Touche Tomasz Woloszynski Pawel Podsiadlo Gwidon W. Stachowiak Juliette Cayer-Barrioz Denis Mazuyer 《Tribology Letters》2017,65(3):113
The effects of depth and top width of transverse rectangular grooves on film thickness and friction in elastohydrodynamic lubrication (EHL) regime were investigated through numerical simulations. Results were obtained in the form of pressure profiles and Stribeck curves for central and minimum film thickness and for friction coefficient. The results indicate that grooves with narrow top widths reduce the minimum film thickness and that this reduction is greater for deeper grooves. Lubricant shearing inside these grooves was further identified as a dominant factor contributing to friction. Near the groove edges, however, no evidence of micro-EHL effect was observed. Based on the results, a groove volume parameter was proposed to characterise the groove lubrication efficiency. We found that the parameter was linearly related to the average central film thickness and by increasing the groove wavelength the film could be made thicker than that of a smooth contact. 相似文献
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传统螺旋槽在背风口处有一处明显的低压区,影响螺旋槽的密封性能。为提高传统螺旋槽的密封性能,在传统螺旋槽的基础上提出一种新型螺旋槽结构。该槽型在传统螺旋槽的背风处一侧并列了一个槽根半径不同短槽,且两槽的槽深相等,形成一个槽根较长的新型螺旋槽结构。通过建立传统螺旋槽与新型螺旋槽的几何模型,利用ANSYS仿真软件对2种槽型进行数值模拟。结果表明,新型螺旋槽的开启力、泄漏量及刚度等干气密封性能均优于传统螺旋槽。对流固耦合下的密封环进行应力、变形分析,对比2种槽型密封环在相同操作参数下的流固耦合应力、变形等的差异。计算结果表明:随着转速与入口压力的增加,2种槽型的动、静环最大应力、变形量均呈现上升趋势,且动环的最大应力、变形量始终大于静环,新型螺旋槽的最大应力、变形量始终大于传统螺旋槽。 相似文献
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A. R. Novoselov A. G. Klimenko 《Optoelectronics, Instrumentation and Data Processing》2014,50(4):407-410
A groove coated with a layer of indium that fills the groove during its formation is generated on the lower surface of sapphire in a single process under the action of laser pulses. The process is performed by using a pulsed gas laser with a wavelength of 0.337 µm. The laser beam is focused through sapphire onto a surface coated with indium. The sapphire motion velocity is uniform, and the sapphire displacement during the time between two pulses is 10% of the light spot diameter. The groove is formed by using the scanning mode (multiple passes of laser radiation through the groove). The pulse energy density in a single pass is sufficiently large. The process is carried out in air. It is found that the optimal option is two passes when the specific resistance of indium in the groove is only 3.8 times greater than the resistance of pure (99.999%) indium bars.. 相似文献
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Densification behavior of tungsten-fiber-reinforced copper powder compacts under hot isostatic pressing was investigated. Hot isostatic pressing was carried out for a bundle of copper-coated tungsten fibers in copper powder. Due to tungsten-fibers and copper coating layers, the densification rate of a tungsten-fiber-reinforced copper powder compact was slower than that of pure copper powder. The constitutive equations by McMeeking and co-workers and by Abouaf and co-workers were implemented into a finite element program (ABAQUS) to analyze densification behavior of tungsten-fiber-reinforced copper powder compacts under hot isostatic pressing. Finite element calculations were compared with experimental results for the variation of relative density with time for copper powder compacts during hot isostatic pressing. Density distributions in copper powder compacts were also investigated by comparing experimental results with finite element calculations. 相似文献
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The provision of helical grooves on the surface of a plain journal bearing should, in principle, improve the overall performance of the bearing. This improvement, however, depends on a number of parameters such as the arrangement of the grooves along the axial length of the bearing. In order to verify this supposition, two types of helical groove bearing with different groove arrangements and a reference plain journal bearing were studied to assess their steady-state performance when lubricated with an oil. It was found that the steady-state performance of both types of helical groove bearing is not as good as that of the plain bearing. Of the two helical groove bearings tested, the asymmetrical bearing proved to be a more energy efficient than the symmetrical bearing. 相似文献
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